How severe is CVE-2026-21438?

CVE-2026-21438 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.

Is CVE-2026-21438 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (29th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-21438?

CVE-2026-21438 affects Quic-go Webtransport-go. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-21438?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-21438 have an EU (EUVD) identifier?

Yes. CVE-2026-21438 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-6719.

When was CVE-2026-21438 published?

CVE-2026-21438 was published on 2026-02-12 and last updated on 2026-06-17.

CVE-2026-21438

CVE-2026-21438 is a medium-severity vulnerability in Quic-go Webtransport-go with a CVSS 3.x base score of 5.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-401.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
EPSS exploit prediction: 0% (29th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-6719
Weakness: CWE-401
Affected product: Quic-go Webtransport-go
Published: 2026-02-12
Last modified: 2026-06-17

Description

webtransport-go is an implementation of the WebTransport protocol. Prior to 0.10.0, an attacker can cause unbounded memory consumption repeatedly creating and closing many WebTransport streams. Closed streams were not removed from an internal session map, preventing garbage collection of their resources. This vulnerability is fixed in v0.10.0.

Frequently asked questions

What is CVE-2026-21438?: webtransport-go is an implementation of the WebTransport protocol. Prior to 0.10.0, an attacker can cause unbounded memory consumption repeatedly creating and closing many WebTransport streams. Closed streams were not removed from an internal session map, preventing garbage collection of their resources. This vulnerability is fixed in v0.10.0.
How severe is CVE-2026-21438?: CVE-2026-21438 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.
Is CVE-2026-21438 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (29th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-21438?: CVE-2026-21438 affects Quic-go Webtransport-go. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-21438?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-21438 have an EU (EUVD) identifier?: Yes. CVE-2026-21438 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-6719.
When was CVE-2026-21438 published?: CVE-2026-21438 was published on 2026-02-12 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:quic-go:webtransport-go:*:*:*:*:*:go:*:*

More vulnerabilities in Quic-go Webtransport-go

CVE-2026-21435 — Medium (CVSS 5.3): webtransport-go is an implementation of the WebTransport protocol. Prior to v0.10.0, an attacker can cause a denial of…
CVE-2026-21434 — Medium (CVSS 5.3): webtransport-go is an implementation of the WebTransport protocol. From 0.3.0 to 0.9.0, an attacker can cause excessive…

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